The air environmental quality of Ma′anshan City in Anhui Province was investigated by using of the Air Pollution Index (API) method. The result showed that the air environmental quality at Ma’anshan City during 1997-2000 was Ⅱ-Ⅰ grade (the air quality is just good), and the critical pollutants were TSP or NOx. Compared with other methods, the usage of API method may accurately reveal and easily calculate the degree of air pollution, and let the local residences and environmental personnel clearly understand the circumstance of air pollution.
